• An organisms that consumes all or part of another organism (prey)
  • benefits its own fitness
  • reduces the growth, fecundity and survival of the prey population

1. True predators: attack, kill & consume

2. Grazers: attack many things, eat only a part and do not kill

3. Parasites: infect one host, keep alive in short term

• Behaviors to capture prey differ vastly
  • consumption rate:
  • consumption rate impacts populations

• True predators and grazers are mostly foragers
  • searching (active)
  • sit and wait (passive)

• Prey behavior (evasiveness) impacts consumption rate

• Parasite rely on transmission
  • direct contact is density dependent

• Obtaining food provides energy

• Searching for and capturing food requires energy

• Foraging is a banking problem: Return on Investment

• To maximize fitness a predator must balance these
  • alpine bumble bees

• Can predators be choosy?
  • Prey densities impact handling/search times

• # of foragers relates to prey density
  • minimize competition
  • group foraging? (Hintz & Lonzarich 2018)

• Predators should choose to forage in a patch with the highest quality

• If they consume the strongest competitor
  • invasive species…

• Relieves competitive pressure on other species enabling coexistence

• Predation structures communities

• Behavior/adaptations of predators and prey
  • natural selection

• Compensatory responses

• Life histories

• Start Simple: Lynx vs Rabbit

1. Start with a lot of rabbits, who does well?
2. Populations of lynx will ….
3. Why does time matter at this step?
4. Populations of prey will….
5. Food for predators will
6. Over time predator populations will ….

• These predator-prey patterns are described in the Lotka-Voltera 2 species model
  • 2 basic components:
  • P = # of predators
  • N = # of prey

• With no predators, prey populations (N) increase exponentially
  • dN/dt = rN
  • r = growth rate

• Predators remove prey at some rate
  • dN/dt = rN - aPN
  • a = attacking efficiency

• Prey stable when dN/dt = 0

• In the absence of food, predator populations (P) will decline
  • dP/dt = -qP
  • q = mortality rate

• Mortality buffered by births (faPN)
  • dP/dt = faPN -qP
  • food gain (aPN)
  • efficiency of food to offspring (f)

• Predator stable when dP/dt = 0